Radiation-sensitive composition and pattern-forming method

ABSTRACT

A radiation-sensitive composition includes particles including a metal oxide as a principal component, a radiation-sensitive acid generator, and an organic solvent. A metal atom constituting the metal oxide includes a first metal atom that is a zinc atom, a boron atom, an aluminum atom, a gallium atom, a thallium atom, a germanium atom, an antimony atom, a bismuth atom, a tellurium atom, or a combination thereof. A van der Waals volume of an acid generated from the radiation-sensitive acid generator is no less than 2.0×10−28 m3. A percentage content of the first metal atom with respect to total metal atoms in the radiation-sensitive composition is no less than 50 atomic %.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional PatentApplication No. 62/297,444, filed Feb. 19, 2016, the contents of whichare incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a radiation-sensitive composition and apattern-forming method.

Discussion of the Background

General radiation-sensitive compositions used for microfabrication bylithography generate acids in regions by irradiation with: extremeultraviolet rays such as an ArF excimer laser beam and a KrF excimerlaser beam; electromagnetic waves such as extreme ultraviolet ray (EUV);charged particle rays such as an electron beam; and the like, making adifference in a rate of dissolution in a developer solution between thelight-exposed regions and light-unexposed regions, through a chemicalreaction in which the acid acts as a catalyst, whereby a pattern isformed on a substrate. The pattern thus formed may be used as a mask andthe like upon processing of the substrate.

Miniaturization in processing techniques has been accompanied by demandsfor improved resist performances of such radiation-sensitivecompositions. To address the demands, types, molecular structures andthe like of polymers, acid generating agents and other components to beused in a composition have been studied, and combinations thereof havealso been extensively studied (refer to Japanese Unexamined PatentApplication, Publication Nos. H11-125907, H8-146610, and 2000-298347).

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a radiation-sensitivecomposition includes particles including a metal oxide as a principalcomponent, a radiation-sensitive acid generator, and an organic solvent.A metal atom constituting the metal oxide includes a first metal atomthat is a zinc atom, a boron atom, an aluminum atom, a gallium atom, athallium atom, a germanium atom, an antimony atom, a bismuth atom, atellurium atom, or a combination thereof. A van der Waals volume of anacid generated from the radiation-sensitive acid generator is no lessthan 2.0×10⁻²⁸ m³. A percentage content of the first metal atom withrespect to total metal atoms in the radiation-sensitive composition isno less than 50 atomic %.

According to another aspect of the present invention, a pattern-formingmethod includes applying the radiation-sensitive composition to form afilm on a substrate. The film is exposed. The film exposed is developed.

DESCRIPTION OF THE EMBODIMENTS

According to an embodiment of the invention, a radiation-sensitivecomponent comprises: particles comprising a metal oxide as a principalcomponent (hereinafter, may be also referred to as “(A) particles” or“particles (A)”); a radiation-sensitive acid generator (hereinafter, maybe also referred to as “(B) acid generator” or “acid generator (B)”);and an organic solvent (hereinafter, may be also referred to as “(C)solvent” or “solvent (C)”), wherein: a metal atom constituting the metaloxide comprises a first metal atom that is a zinc atom, a boron atom, analuminum atom, a gallium atom, a thallium atom, a germanium atom, anantimony atom, a bismuth atom, a tellurium atom, or a combinationthereof; and a van der Waals volume of an acid generated from theradiation-sensitive acid generator is no less than 2.0×10⁻²⁸ m³; and apercentage content of the first metal atom with respect to total metalatoms in the composition is no less than 50 atomic %.

According to another embodiment of the present invention made forsolving the aforementioned problems, a pattern-forming method comprises:applying the radiation-sensitive composition on one face side of asubstrate; exposing a film obtained by the applying; and developing thefilm exposed.

The term “metal oxide” as referred to means a compound that comprises atleast a metal atom and an oxygen atom. The term “principal component” asreferred to means a component which is of the highest content, forexample, a component the content of which is no less than 50% by mass.The term “particles” as referred to means, for example, a substance thathas an average particle diameter of no less than 1 nm. The term “totalmetal atoms” as referred to is a concept encompassing metalloid atoms.The term “metalloid atom” as referred to means a boron atom, a siliconatom, a germanium atom, an arsenic atom, an antimony atom, and atellurium atom.

The radiation-sensitive composition and the pattern-forming methodaccording to the embodiments of the present invention enable a patternsuperior in resolution to be formed with high sensitivity. Therefore,these can be suitably used for a processing process of semiconductordevices, and the like, in which further progress of miniaturization isexpected in the future. Hereinafter, the embodiments will be explainedin detail.

Radiation-Sensitive Composition

The radiation-sensitive composition comprises (A) particles, (B) an acidgenerator, and (C) a solvent. The composition for film formation mayfurther contain other optional component within a range not leading toimpairment of the effects of the present invention. The metal atomconstituting the metal oxide, which is the principal component of theparticles (A), comprises the first metal atom that is a zinc atom, aboron atom, an aluminum atom, a gallium atom, a thallium atom, agermanium atom, an antimony atom, a bismuth atom, a tellurium atom, or acombination thereof. A van der Waals volume of an acid generated fromthe acid generator (B) is no less than 2.0×10⁻²⁸ m³. A percentagecontent of the first metal atom with respect to total metal atoms in theradiation-sensitive composition is no less than 50 atomic %.

Due to comprising the particles (A), the acid generator (B) and thesolvent (C), with the van der Waals volume of an acid generated from theacid generator (B) being no less than the lower limit, and thepercentage content of the first metal atom with respect to total metalatoms in the composition being no less than the lower limit, theradiation-sensitive composition enables a pattern superior in resolutionto be formed with high sensitivity. Although not necessarily clarified,the reason for achieving the effects described above due to theradiation-sensitive composition having the aforementioned constitutionis inferred as in the following, for example. Specifically, in a filmformed from the radiation-sensitive composition, the first metal atomcomprised in the particles (A) and the like in the light-exposed regionsabsorbs exposure light and releases secondary electrons, and then anacid is generated from the acid generator (B) by an action of thesecondary electrons and the like. The acid accelerates a structuralchange of the particles (A) to change a solubility in a developersolution, thereby enabling a pattern to be formed on the film. Here, thefirst metal atom is more likely to release the secondary electrons thanother metal atoms such as transition metal atoms. Meanwhile, theparticles (A) that comprise as a principal component a metal oxidecomprising the first metal atom are likely to have a solubility in adeveloper solution appropriately changed by virtue of the acid.Furthermore, the acid generator (B) is capable of appropriatelyinhibiting a diffusion phenomenon of the acid in the film by virtue ofthe comparatively great van der Waals volume of the acid to begenerated, thereby enabling inhibition of unwanted chemical reactions inthe light-unexposed regions. Moreover, since the percentage content ofthe first metal atom with respect to total metal atoms is no less thanthe lower limit, the radiation-sensitive composition enables the releaseof the secondary electrons by the first metal atom to be sufficientlypromoted. It is considered that, as a result of these features, theradiation-sensitive composition is superior in sensitivity andresolution.

The lower limit of the percentage content of the first metal atom withrespect to total metal atoms in the radiation-sensitive composition is50 atomic %, preferably 80 atomic %, more preferably 95 atomic %, andfurther more preferably 99 atomic %. Due to the percentage content ofthe first metal atom being no less than the lower limit, more effectivepromotion of the release of the secondary electrons by the first metalatom is enabled, whereby the sensitivity and resolution of theradiation-sensitive composition can be further improved.

(A) Particles

The particles (A) comprise a metal oxide as a principal component. It isto be noted that since the particles (A) comprise the metal oxide as theprincipal component, the particles (A) contribute also to improvingetching resistance of a pattern formed from the radiation-sensitivecomposition.

The lower limit of an average particle diameter of the particles (A) ispreferably 1.1 nm, and more preferably 1.2 nm. Meanwhile, the upperlimit of the average particle diameter is preferably 20 nm, morepreferably 10 nm, further more preferably 3.0 nm, and particularlypreferably 2.5 nm. When the average particle diameter of the particles(A) falls within the above range, more effective promotion of thegeneration of the secondary electrons by the particles (A) is enabled,whereby the sensitivity and resolution of the radiation-sensitivecomposition can be further improved. The “average particle diameter” asreferred to means a harmonic mean particle size on the basis ofscattered light intensity, as measured by DLS (Dynamic Light Scattering)using a light scattering measurement device.

Metal Oxide

The metal atom constituting the metal oxide, which is the principalcomponent of the particles (A), comprises the first metal atom that is azinc atom, a boron atom, an aluminum atom, a gallium atom, a thalliumatom, a germanium atom, an antimony atom, a bismuth atom, a telluriumatom, or a combination thereof. The lower limit of the percentagecontent of the first metal atom with respect to total metal atomsconstituting the metal oxide is preferably 50 atomic %, more preferably80 atomic %, and further more preferably 99 atomic %. When thepercentage content of the first metal atom is no less than the lowerlimit, release of the secondary electrons in the light-exposed regionsof the film formed from the radiation-sensitive composition, and changeof solubility of the particles (A) in a developer solution by the acidgenerated from the acid generator (B) are enabled to be furtherpromoted, thereby enabling the sensitivity and resolution of theradiation-sensitive composition to be further improved. It is to benoted that the percentage content of the first metal atom contained mayalso be 100 atomic %.

As the first metal atom, a zinc atom and a metalloid atom are preferred,and a zinc atom and an antimony atom are more preferred. By using thesemetal atoms as the first metal atom, further improvements of thesensitivity and resolution of the radiation-sensitive composition areenabled. Either one type, or a combination of two or more types, ofthese metal atoms may be used as the first metal atom.

The metal oxide may contain an additional atom, other than the metalatom and the oxygen atom. Examples of the additional atom include acarbon atom, a hydrogen atom, a nitrogen atom, a phosphorus atom, asulfur atom, a halogen atom, and the like.

The lower limit of a total percentage content of the metal atom and theoxygen atom in the metal oxide is preferably 5% by mass, more preferably10% by mass, and further more preferably 25% by mass. Meanwhile, theupper limit of the total percentage content of the metal atom and theoxygen atom in the metal oxide is preferably 99.9% by mass, morepreferably 80% by mass, and further more preferably 70% by mass. Whenthe total percentage content of the metal atom and the oxygen atom fallswithin the above range, more effective promotion of the generation ofthe secondary electrons by the particles (A) is enabled to, whereby thesensitivity of the radiation-sensitive composition can be furtherimproved. It is to be noted that the total percentage content of themetal atom and the oxygen atom may also be 100% by mass.

The metal oxide is exemplified by: a metal oxide constituted only of ametal atom and an oxygen atom; a metal oxide comprising a metal atom andan organic ligand; and the like. Exemplary metal oxide comprising ametal atom and an organic ligand is a molecule comprising a repeatingstructure of: (metal atom-organic ligand-metal atom). As the organicligand, a ligand derived from (a) an organic acid is preferred.Exemplary ligand derived from the organic acid (a) is an anion generatedby eliminating one or a plurality of protons from the organic acid (a).The “organic acid” as referred to means an acidic organic compound, andthe “organic compound” as referred to means a compound having at leastone carbon atom.

When the particles (A) comprising as a principal component the metaloxide that comprises the metal atom and the ligand derived from theorganic acid (a), further improvements of the sensitivity and resolutionof the radiation-sensitive composition are enabled. Although notnecessarily clarified, the reason for achieving the effects describedabove due to the radiation-sensitive composition having theaforementioned constitution is inferred as in the following, forexample. Specifically, it is considered that the ligand derived from theorganic acid (a) is present in the vicinity of a surface of theparticles (A) due to an interaction with the metal atom, to therebyimprove the solubility of the particles (A) in a developer solution.Meanwhile, it is considered that in the light-exposed regions of thefilm formed from the radiation-sensitive composition, the ligand derivedfrom the organic acid (a) is eliminated from the particles (A) due to astructural change of the particles (A), whereby the solubility of theparticles (A) in a developer solution is changed more greatly. Thesensitivity and resolution of the radiation-sensitive composition areconsidered to be further improved as a result of the foregoing.

The lower limit of pKa of the organic acid (a) is preferably 0, morepreferably 1, further more preferably 1.5, and particularly preferably2. Meanwhile, the upper limit of the pKa is preferably 7, morepreferably 6, further more preferably 5.5, and particularly preferably5. When the pKa of the organic acid (a) falls within the above range, itis possible to adjust the interaction between the ligand derived fromthe organic acid (a) and the metal atom to be moderately weak, wherebyfurther improvements of the sensitivity and resolution of theradiation-sensitive composition are enabled. Here, in the case of theorganic acid (a) being a polyvalent acid, the pKa of the organic acid(a) as referred to means a primary acid dissociation constant, i.e., alogarithmic value of a dissociation constant for dissociation of thefirst proton.

The organic acid (a) may be either a low molecular weight compound or ahigh molecular weight compound, and a low molecular weight compound ispreferred in light of adjusting the interaction with the metal atom tobe more appropriately weak. The “low molecular weight compound” asreferred to means a compound having a molecular weight of no greaterthan 1,500, whereby the “high molecular weight compound” as referred tomeans a compound having a molecular weight of greater than 1,500. Thelower limit of the molecular weight of the organic acid (a) ispreferably 50, and more preferably 70. Meanwhile, the upper limit of themolecular weight is preferably 1,000, more preferably 500, further morepreferably 400, and particularly preferably 300. When the molecularweight of the organic acid (a) falls within the above range, it ispossible to adjust solubility of the particles (A) in a developersolution to be more appropriate, whereby the sensitivity and resolutionof the radiation-sensitive composition can be further improved.

The organic acid (a) is exemplified by a carboxylic acid, a sulfonicacid, a sulfinic acid, an organic phosphinic acid, an organic phosphonicacid, a phenol, an enol, a thiol, an acid imide, an oxime, asulfonamide, and the like.

Examples of the carboxylic acid include:

monocarboxylic acids such as formic acid, acetic acid, propionic acid,butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoicacid, nonanoic acid, decanoic acid, 2-ethylhexanoic acid, tiglic acid,oleic acid, acrylic acid, methacrylic acid, trans-2,3-dimethylacrylicacid, stearic acid, linoleic acid, linolenic acid, arachidonic acid,salicylic acid, benzoic acid, p-aminobenzoic acid, iodobenzoic acid(such as 2-iodobenzoic acid, 3-iodobenzoic acid and 4-iodobenzoic acid),monochloroacetic acid, dichloroacetic acid, trichloroacetic acid,o-toluic acid, m-toluic acid, p-toluic acid, trifluoroacetic acid,pentafluoropropionic acid, gallic acid and shikimic acid;

dicarboxylic acids such as oxalic acid, malonic acid, maleic acid,methylmalonic acid, fumaric acid, adipic acid, sebacic acid, phthalicacid and tartaric acid;

carboxylic acids having no less than 3 carboxy groups such as citricacid; and the like.

Examples of the sulfonic acid include benzenesulfonic acid,p-toluenesulfonic acid, and the like.

Examples of the sulfinic acid include benzenesulfinic acid,p-toluenesulfinic acid, and the like.

Examples of the organic phosphinic acid include diethylphosphinic acid,methylphenylphosphinic acid, diphenylphosphinic acid, and the like.

Examples of the organic phosphonic acid include methylphosphonic acid,ethylphosphonic acid, t-butylphosphonic acid, cyclohexylphosphonic acid,phenylphosphonic acid, and the like.

Examples of the phenol include: monovalent phenols such as phenol,cresol, 2,6-xylenol, and naphthol;

divalent phenols such as catechol, resorcinol, hydroquinone and1,2-naphthalenediol;

phenols having a valency of no less than 3 such as pyrogallol and2,3,6-naphthalenetriol; and the like.

Examples of the enol include 2-hydroxy-3-methyl-2-butene,3-hydroxy-4-methyl-3-hexene, and the like.

Examples of the thiol include mercaptoethanol, mercaptopropanol, and thelike.

Examples of the acid imide include:

carboxylic imides such as maleimide and succinimide;

sulfonic imides such as a di(trifluoromethanesulfonic acid) imide anddi(pentafluoroethanesulfonic acid) imide; and the like.

Examples of the oxime include:

aldoximes such as benzaldoxime and salicylaldoxime;

ketoximes such as diethylketoxime, methylethylketoxime andcyclohexanoneoxime; and the like.

Examples of the sulfonamide include methylsulfonamide, ethylsulfonamide,benzenesulfonamide, toluenesulfonamide, and the like.

In light of further improving the sensitivity and resolution of theradiation-sensitive composition, as the organic acid (a), the carboxylicacid is preferred; the monocarboxylic acid is more preferred; andmethacrylic acid, tiglic acid, benzoic acid and m-toluic acid arefurther more preferred.

As the metal oxide, a metal oxide comprising zinc and a ligand derivedfrom methacrylic acid; a metal oxide comprising zinc and a ligandderived from benzoic acid; a metal oxide comprising zinc and a ligandderived from tiglic acid; a metal oxide comprising bismuth and a ligandderived from methacrylic acid; a metal oxide comprising tellurium and aligand derived from methacrylic acid; a metal oxide comprising germaniumand a ligand derived from benzoic acid; a metal oxide comprising boronand a ligand derived from benzoic acid; a metal oxide comprisingaluminum and a ligand derived from benzoic acid; a metal oxidecomprising gallium and a ligand derived from tiglic acid; a metal oxidecomprising thallium and a ligand derived from tiglic acid; a metal oxideconstituted of zinc and oxygen atoms; and a metal oxide comprisingantimony and a ligand derived from tiglic acid are preferred, amongwhich the metal oxide comprising zinc and a ligand derived from benzoicacid is more preferred.

The lower limit of a percentage content of the metal oxide in theparticles (A) is preferably 60% by mass, more preferably 80% by mass,and further more preferably 95% by mass. It is to be noted that thepercentage content of the metal oxide may also be 100% by mass. When thepercentage content of the metal oxide is no less than the lower limit,further improvements of the sensitivity and resolution of theradiation-sensitive composition are enabled. The particles (A) mayinclude either only a single type, or two or more types, of the metaloxides.

The lower limit of the number of the first metal atoms comprised in theparticles (A) is preferably 2, and more preferably 4. Meanwhile, theupper limit of the number of the first metal atoms comprised in theparticles (A) is preferably 30, more preferably 10, and further morepreferably 6. When the number of the first metal atoms comprised in theparticles (A) falls within the above range, further improvements of thesensitivity and resolution of the radiation-sensitive composition areenabled.

In the case of the particles (A) comprising the ligand derived from theorganic acid (a), the lower limit of the percentage content of theligand derived from the organic acid (a) in the particles (A) ispreferably 1% by mass, more preferably 20% by mass, further morepreferably 40% by mass, and particularly preferably 60% by mass.Meanwhile, the upper limit of the percentage content of the ligandderived from the organic acid (a) is preferably 95% by mass, and morepreferably 90% by mass. When the percentage content of the ligandderived from the organic acid (a) falls within the above range, it ispossible to adjust solubility of the particles (A) in a developersolution to be more appropriate, whereby further improvements of thesensitivity and resolution of the radiation-sensitive composition areenabled. The particles (A) may include either only a single type, or twoor more types, of the ligand derived from the organic acid (a).

The lower limit of the content of the particles (A) with respect to thetotal solid content in the composition is preferably 10% by mass, morepreferably 50% by mass, further more preferably 70% by mass, andparticularly preferably 85% by mass. Meanwhile, the upper limit of thecontent of the particles (A) with respect to the total solid content inthe composition is preferably 99% by mass, and more preferably 95% bymass. When the content of the particles (A) falls within the aboverange, further improvements of the sensitivity and resolution of theradiation-sensitive composition are enabled. The radiation-sensitivecomposition may include either only a single type, or two or more types,of the particles (A). The “solid content” as referred to means acomponent obtained by removing the solvent (C) and an inorganic solvent(described later) from the radiation-sensitive composition.

Synthesis Procedure of (A) Particles

The particles (A) may be obtained by, for example, a procedure ofcarrying out a hydrolytic condensation reaction by using (b) ametal-containing compound (described later), a procedure of carrying outa ligand substitution reaction by using the metal-containing compound(b), and the like. The “hydrolytic condensation reaction” as referred tomeans a reaction in which a hydrolyzable group comprised in themetal-containing compound (b) is hydrolyzed to give —OH, and two —OHsthus obtained undergo dehydrative condensation to form —O—.

Metal-Containing Compound (b)

The metal-containing compound (b) is: a metal compound (I) comprisingthe first metal atom and a hydrolyzable group; a hydrolysis product ofthe metal compound (I) comprising the first metal atom and ahydrolyzable group; a hydrolytic condensation product of the metalcompound (I) comprising the first metal atom and a hydrolyzable group;or a combination thereof. The metal compound (I) may be used eitheralone of one type, or in combination of two or more types thereof.

The hydrolyzable group is exemplified by a halogen atom, an alkoxygroup, an acyloxy group, and the like.

Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom, an iodine atom, and the like.

Examples of the alkoxy group include a methoxy group, an ethoxy group, an-propoxy group, an i-propoxybutoxy group, and the like.

Examples of the acyloxy group include an acetoxy group, an ethylyloxygroup, a propionyloxy group, a butyryloxy group, a t-butyryloxy group, at-amylyloxy group, a n-hexanecarbonyloxy group, a n-octanecarbonyloxygroup, and the like.

As the hydrolyzable group, an alkoxy group and an acyloxy group arepreferred, and an isopropoxy group and an acetoxy group are morepreferred.

The metal compound (I) is exemplified by compounds represented by thefollowing formula (1) (hereinafter, may be also referred to as a “metalcompound (I-1)”), and the like. By using the metal compound (I-1),forming a stable metal oxide is enabled, whereby further improvements ofthe sensitivity and resolution of the radiation-sensitive compositionare enabled.L_(a)MY_(b)  (1)

In the above formula (1), M represents the first metal atom; Lrepresents a ligand; a is an integer of 0 to 2, wherein in a case wherea is 2, a plurality of Ls are identical or different; Y represents thehydrolyzable group selected from a halogen atom, an alkoxy group, and anacyloxy group; and b is an integer of 2 to 6, wherein a plurality of Ysmay be identical or different, and L is a ligand that does not fallunder the definition of Y.

As the first metal atom represented by M, a bismuth atom, a zinc atom,and a tellurium atom are preferred.

The ligand represented by L is exemplified by a monodentate ligand and apolydentate ligand.

Exemplary monodentate ligand includes a hydroxo ligand, a carboxyligand, an amido ligand, an amine ligand, a nitro ligand, ammonia, andthe like.

Examples of the amido ligand include an unsubstituted amido ligand(NH₂), a methylamido ligand (NHMe), a dimethylamido ligand (NMe₂), adiethylamido ligand (NEt₂), a dipropylamido ligand (NPr₂), and the like.Examples of the amine ligand include a trimethylamine ligand, atriethylamine ligand, and the like.

Exemplary polydentate ligand includes a hydroxy acid ester, aβ-diketone, a β-keto ester, a β-dicarboxylic acid ester, a hydrocarbonhaving a π bond, a diphosphine, and the like.

Examples of the hydroxy acid ester include glycolic acid esters, lacticacid esters, 2-hydroxycyclohexane-1-carboxylic acid esters, salicylicacid esters, and the like.

Examples of the β-diketone include 2,4-pentanedione,3-methyl-2,4-pentanedione, 3-ethyl-2,4-pentanedione, and the like.

Examples of the β-keto ester include acetoacetic acid esters,α-alkyl-substituted acetoacetic acid esters, β-ketopentanoic acidesters, benzoylacetic acid esters, 1,3-acetonedicarboxylic acid esters,and the like.

Examples of the β-dicarboxylic acid ester include malonic acid diesters,α-alkyl-substituted malonic acid diesters, α-cycloalkyl-substitutedmalonic acid diesters, α-aryl-substituted malonic acid diesters, and thelike.

Examples of the hydrocarbon having a π bond include:

chain olefins such as ethylene and propylene;

cyclic olefins such as cyclopentene, cyclohexene and norbornene;

chain dienes such as butadiene and isoprene;

cyclic dienes such as cyclopentadiene, methylcyclopentadiene,pentamethylcyclopentadiene, cyclohexadiene and norbornadiene;

aromatic hydrocarbons such as benzene, toluene, xylene,hexamethylbenzene, naphthalene and indene; and the like.

Examples of the diphosphine includes 1,1-bis(diphenylphosphino)methane,1,2-bis(diphenylphosphino)ethane, 1,3-bis(diphenylphosphino)propane,2,2′-bis(diphenylphosphino)-1,1′-binaphthyl,1,1′-bis(diphenylphosphino)ferrocene, and the like.

Examples and preferred examples of the halogen atom, the alkoxy group,and the acyloxy group which may be represented by Y may be similar tothose exemplified in connection with the hydrolyzable group.

Preferably b is an integer of 2 to 4. When b is the above specifiedvalue, it is possible to increase the percentage content of the metaloxide in the particles (A), whereby more effective promotion of thegeneration of the secondary electrons by the particles (A) is enabled.Consequently, a further improvement of the sensitivity of theradiation-sensitive composition is enabled.

As the metal-containing compound (b), a metal alkoxide that is neitherhydrolyzed nor hydrolytic condensed, and a metal acyloxide that isneither hydrolyzed nor hydrolytically condensed are preferred.

Examples of the metal-containing compound (b) include bismuth(III)isopropoxide, tellurium(IV) aisopropoxide, zinc(II) isopropoxide, zincacetate dihydrate, germanium(IV) isopropoxide, boron(III) ethoxide,aluminum(III) isopropoxide, gallium(III) isopropoxide, thallium(I)ethoxide, antimony(III) ethoxide, antimony(III) isopropoxide, and thelike. Of these, compounds comprising at least one of zinc and antimonyare preferred; and zinc acetate dihydrate and antimony(III) isopropoxideare more preferred, as the metal-containing compound (b).

A procedure for carrying out the hydrolytic condensation reaction usingthe metal-containing compound (b) may be exemplified by: a procedure ofhydrolytically condensing the metal-containing compound (b) in a solventcontaining water; and the like. In this case, other compound having ahydrolyzable group may be added as needed. The lower limit of the amountof water used for the hydrolytic condensation reaction is preferably 0.2times molar amount, more preferably an equimolar amount, and furthermore preferably 3 times molar amount with respect to the hydrolyzablegroup comprised in the metal-containing compound (b) and the like. Theupper limit of the amount of water is preferably 20 times molar amount,more preferably 15 times molar amount, and further more preferably 10times molar amount. When the amount of the water in the hydrolyticcondensation reaction falls within the above range, it is possible toincrease the percentage content of the metal oxide in the particles (A)to be obtained, whereby further improvements of the sensitivity andresolution of the radiation-sensitive composition are enabled. It is tobe noted that, the hydrolytic condensation reaction may proceed evenwith a small amount of water having been inevitably contaminated into inthe solvent, and it is therefore not necessarily required to especiallyadd water into the solvent.

A procedure for carrying out the ligand substitution reaction using themetal-containing compound (b) may be exemplified by: a procedure ofmixing the metal-containing compound (b) and the organic acid (a); andthe like. In this case, mixing of the metal-containing compound and theorganic acid (a) may be performed either in a solvent or without asolvent. Upon the mixing, a base such as triethylamine may be added asneeded. An amount of the base added is, for example, no less than 1 partby mass and no greater than 200 parts by mass with respect to 100 partsby mass of a total amount of the metal-containing compound (b) and theorganic acid (a) used.

In the case of using an organic acid for synthesizing the particles (A),the lower limit of the amount of the organic acid used is preferably 10parts by mass, and more preferably 30 parts by mass, with respect to 100parts by mass of the metal-containing compound (b). Meanwhile, the upperlimit of the amount of the organic acid used is preferably 2,000 partsby mass, more preferably 1,000 parts by mass, further more preferably700 parts by mass, and particularly preferably 100 parts by mass, withrespect to 100 parts by mass of the metal-containing compound (b). Whenthe amount of the organic acid used falls within the above range, it ispossible to appropriately adjust a percentage content of the ligandderived from the organic acid (a) in the particles (A) to be obtained,whereby further improvements of the sensitivity and resolution of theradiation-sensitive composition are enabled.

Upon the synthesis reaction of the particles (A), in addition to themetal compound (I) and the organic acid (a), a compound that may be thepolydentate ligand represented by L in the compound of the formula (1),a compound that may be a bridging ligand, etc., may also be added.Examples of the compound that may be a bridging ligand include:compounds having two or more coordinating groups such as a hydroxygroup, an isocyanate group, an amino group, an ester group, an amidegroup, etc.; and the like.

The solvent for use in the synthesis reaction of the particles (A) isnot particularly limited, and solvents similar to those exemplified inconnection with the solvent (C) described later may be used. Of these,alcohol solvents, ether solvents, ester solvents, and hydrocarbonsolvents are preferred; ether solvents and ester solvents are morepreferred; cyclic ether solvents and monocarboxylic acid ester solventsare further more preferred; and tetrahydrofuran and ethyl acetate areparticularly preferred.

In the case of using the solvent in the synthesis reaction of theparticles (A), the solvent used may be either removed after thecompletion of the reaction, or directly used as the solvent (C) in theradiation-sensitive composition without removal thereof.

The lower limit of the temperature of the synthesis reaction of theparticles (A) is preferably 0° C., and more preferably 10° C. The upperlimit of the temperature is preferably 150° C., and more preferably 100°C.

The lower limit of the time period of the synthesis reaction of theparticles (A) is preferably 1 min, more preferably 10 min, and furthermore preferably 1 hour. The upper limit of the time period is preferably100 hrs, more preferably 50 hrs, and further more preferably 24 hrs.

(B) Acid Generator

The acid generator (B) to be used in the radiation-sensitive compositionis a component that generates an acid having a van der Waals volume ofno less than 2.0×10⁻²⁸ m³ upon irradiation with a radioactive ray. Theacid generator (B) may be contained in the radiation-sensitivecomposition in the form of a low molecular weight compound (hereinafter,may be also referred to as “(B) acid generating agent” as appropriate),or in the form incorporated as a part of a polymer, or in both of theseforms; however, it is preferred that only the acid generating agent (B)is contained, in light of etching resistance.

The lower limit of the van der Waals volume of the acid generated fromthe acid generator (B) is preferably 3.0×10⁻²⁸ m³. Meanwhile, the upperlimit of the van der Waals volume of the acid generated from the acidgenerator (B) is preferably 8.0×10⁻²⁸ m³, and more preferably 6.0×10⁻²⁸m³. When the van der Waals volume of the acid falls within the aboverange, further improvements of the sensitivity and resolution of theradiation-sensitive composition are enabled. The term “van der Waalsvolume” as referred to means a volume occupied by a van der Waals sphereon the basis of a van der Waals radius of the atoms constituting theacid, the volume being calculated by obtaining a stable structure inaccordance with the PM3 method using molecular orbital calculationsoftware.

The acid generating agent (B) is exemplified by an onium salt compound,a N-sulfonyloxyimide compound, a halogen-containing compound, a diazoketone compound, and the like.

Exemplary onium salt compound includes a sulfonium salt, atetrahydrothiophenium salts, an iodonium salt, a phosphonium salt, adiazonium salt, a pyridinium salt, and the like.

Examples of the sulfonium salt include triphenylsulfoniumperfluoro-n-octanesulfonate, triphenylsulfonium2-bicyclo[2.2.1]hept-2-yl-1,1,2,2,-tetrafluoroethanesulfonate,triphenylsulfonium camphorsulfonate, triphenylsulfonium6-(adamantane-1-ylcarbonyloxy)-1,1,2,2-tetrafluorohexane-1-sulfonate,triphenylsulfonium 2-(1-adamantyl)-1,1-difluoroethanesulfonate,triphenylsulfonium2-(adamantane-1-ylcarbonyloxy)-1,1,3,3,3-pentafluoropropane-1-sulfonate,triphenylsulfonium2-(4-oxoadamantane-1-ylcarbonyloxy)-1,1,3,3,3-pentafluoropropane-1-silfonate,triphenylsulfonium 1,2-di(cyclohexyloxycarbonyl)ethane-1-sulfonate,4-cyclohexylphenyldiphenylsulfonium perfluoro-n-octanesulfonate,4-cyclohexylphenyldiphenylsulfonium2-bicyclo[2.2.1]hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate,4-cyclohexylphenyldiphenylsulfonium camphorsulfonate,4-methanesulfonylphenyldiphenylsulfonium perfluoro-n-octanesulfonate,4-methanesulfonylphenyldiphenylsulfonium2-bicyclo[2.2.1]hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate,4-methanesulfonylphenyldiphenylsulfonium camphorsulfonate,4-cyclohexylsulfonylphenyldiphenylsulfonium5,6-di(cyclohexyloxycarbonyl)norbornane-2-sulfonate, and the like.

Examples of the tetrahydrothiophenium salt include1-(4-n-butoxynaphthalen-1-yl)tetrahydrothiopheniumperfluoro-n-octanesulfonate,1-(4-n-butoxynaphthalen-1-yl)tetrahydrothiophenium2-bicyclo[2.2.1]hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate,1-(4-n-butoxynaphthalen-1-yl)tetrahydrothiophenium camphorsulphonate,1-(4-n-butoxynaphthalen-1-yl)tetrahydrothiophenium hexafluoropropylenesulfonimide, 1-(6-n-butoxynaphthalen-2-yl)tetrahydrothiopheniumperfluoro-n-octanesulfonate,1-(6-n-butoxynaphthalen-2-yl)tetrahydrothiophenium2-bicyclo[2.2.1]hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate,1-(6-n-butoxynaphthalen-2-yl)tetrahydrothiophenium camphorsulphonate,1-(6-n-butoxynaphthalen-2-yl)tetrahydrothiophenium hexafluoropropylenesulfonimide, 1-(3,5-dimethyl-4-hydroxyphenyl)tetrahydrothiopheniumperfluoro-n-octanesulfonate,1-(3,5-dimethyl-4-hydroxyphenyl)tetrahydrothiophenium2-bicyclo[2.2.1]hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate,1-(3,5-dimethyl-4-hydroxyphenyl)tetrahydrothiophenium camphorsulfonate,1-(3,5-dimethyl-4-hydroxyphenyl)tetrahydrothiopheniumtetrahydrothiophenium hexafluoro propylene sulfonimide, and the like.

Examples of the iodonium salt include diphenyliodoniumperfluoro-n-octanesulfonate, diphenyliodonium2-bicyclo[2.2.1]hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate,diphenyliodonium camphorsulfonate, bis(4-t-butylphenyl)iodoniumperfluoro-n-octanesulfonate, bis(4-t-butylphenyl)iodonium2-bicyclo[2.2.1]hept-2-yl-1,1,2,2-tetrafluoroethanesulfonate,bis(4-t-butylphenyl)iodonium camphorsulfonate, and the like.

Examples of the N-sulfonyloxyimide compound includeN-(trifluoromethanesulfonyloxy)bicyclo[2.2.1]hept-5-ene-2,3-dicarboxyimide,N-(nonafluoro-n-butanesulfonyloxy)bicyclo[2.2.1]hept-5-ene-2,3-dicarboxyimide,N-(perfluoro-n-octanesulfonyloxy)bicyclo[2.2.1]hept-5-ene-2,3-dicarboxyimide,N-(2-bicyclo[2.2.1]hept-2-yl-1,1,2,2-tetrafluoroethanesulfonyloxy)bicyclo[2.2.1]hept-5-ene-2,3-dicarboxyimide,N-(2-(3-tetracyclo[4.4.0.1^(2,5),1^(7,10)]dodecanyl)-1,1-difluoroethanesulfonyloxy)bicyclo[2.2.1]hept-5-ene-2,3-dicarboxyimide,N-(camphorsulfonyloxy)bicyclo[2.2.1]hept-5-ene-2,3-dicarboxyimide, andthe like.

As the acid generating agent (B), an onium salt compound is preferred, asulfonium salt is more preferred, and triphenylsulfonium6-(adamantane-1-ylcarbonyloxy)-1,1,2,2-tetrafluorohexane-1-sulfonate and4-cyclohexylsulfonylphenyldiphenylsulfonium5,6-di(cyclohexyloxycarbonyl)norbornane-2-sulfonate are particularlypreferred.

In the case in which the radiation-sensitive composition contains theacid generating agent (B) as the acid generator (B), the lower limit ofthe content of the acid generating agent (B) with respect to the totalsolid content in the composition is preferably 1% by mass, morepreferably 2% by mass, and further more preferably 3% by mass.Meanwhile, the upper limit of the content of the acid generating agent(B) with respect to the total solid content in the composition ispreferably 40% by mass, more preferably 30% by mass, and further morepreferably 20% by mass. When the content of the acid generating agent(B) falls within the above range, further improvements of thesensitivity and resolution of the radiation-sensitive composition areenabled. The radiation-sensitive composition may include either only asingle type, or two or more types, of the acid generating agent (B).

(C) Solvent

The solvent (C) used in the radiation-sensitive composition is notparticularly limited as long as it is a solvent capable of dissolving ordispersing at least the particles (A), the acid generator (B), as wellas optional component(s) comprised as needed. The solvent used in thesynthesis of the particles (A) may also be directly used as the solvent(C). The radiation-sensitive composition may include either only asingle type, or two or more types, of the solvent (C). It is to be notedthat although the radiation-sensitive composition may further comprisean inorganic solvent such as water in addition to the solvent (C), it ispreferred that the inorganic solvent is not contained as a principalsolvent, in light of applicability to a substrate, solubility of theparticles (A) in a developer solution, storage stability, etc. The upperlimit of the content of the inorganic solvent in the radiation-sensitivecomposition is preferably 20 parts by mass, and more preferably 10 partsby mass.

The solvent (C) is exemplified by an alcohol solvent, an ether solvent,a ketone solvent, an amide solvent, an ester solvent, a hydrocarbonsolvent, and the like.

Examples of the alcohol solvent include:

aliphatic monohydric alcohol solvents having 1 to 18 carbon atoms suchas ethanol, 2-propanol, 4-methyl-2-pentanol and n-hexanol;

alicyclic monohydric alcohol solvents having 3 to 18 carbon atoms suchas cyclohexanol;

polyhydric alcohol solvents having 2 to 18 carbon atoms such as1,2-propylene glycol;

polyhydric alcohol partial ether solvents having 3 to 19 carbon atomssuch as propylene glycol monomethyl ether and propylene glycol monoethylether; and the like.

Examples of the ether solvent include:

dialkyl ether solvents such as diethyl ether, dipropyl ether, dibutylether, dipentyl ether, diisoamyl ether, dihexyl ether and diheptylether;

cyclic ether solvents such as tetrahydrofuran and tetrahydropyran;

aromatic ring-containing ether solvents such as diphenyl ether andanisole; and the like.

Examples of the ketone solvent include:

chain ketone solvents such as acetone, methyl ethyl ketone, methyln-propyl ketone, methyl n-butyl ketone, diethyl ketone, methyl iso-butylketone, 2-heptanone, ethyl n-butyl ketone, methyl n-hexyl ketone,di-iso-butyl ketone and trimethylnonanone;

cyclic ketone solvents such as cyclopentanone, cyclohexanone,cycloheptanone, cyclooctanone and methylcyclohexanone;

2,4-pentanedione, acetonylacetone and acetophenone; and the like.

Examples of the amide solvent include:

cyclic amide solvents such as N,N′-dimethylimidazolidinone andN-methylpyrrolidone;

chain amide solvents such as N-methylformamide, N,N-dimethylformamide,N,N-diethylformamide, acetamide, N-methylacetamide,N,N-dimethylacetamide and N-methylpropionamide; and the like.

Examples of the ester solvent include:

monocarboxylic acid ester solvents such as ethyl acetate, n-butylacetate and ethyl lactate;

polyhydric alcohol carboxylate solvents such as propylene glycolacetate;

polyhydric alcohol partial ether carboxylate solvents such as propyleneglycol monomethyl ether acetate and propylene glycol monoethyl etheracetate;

polyhydric carboxylic acid diester solvents such as diethyl oxalate;

lactone solvents such as γ-butyrolactone and δ-valerolactone;

carbonate solvents such as dimethyl carbonate, diethyl carbonate,ethylene carbonate and propylene carbonate; and the like.

Examples of the hydrocarbon solvent include:

aliphatic hydrocarbon solvents having 5 to 12 carbon atoms such asn-pentane and n-hexane;

alicyclic hydrocarbon solvents having 5 to 12 ring atoms such asdecahydronaphthalene;

aromatic hydrocarbon solvents having 6 to 16 carbon atoms such astoluene and xylene; and the like.

As the solvent (C), an alcohol solvent and an ester solvent arepreferred; a polyhydric alcohol partial ether solvent and a polyhydricalcohol partial ether carboxylate solvent are preferred; and propyleneglycol monoethyl ether and propylene glycol monomethyl ether acetate arefurther more preferred.

Other Optional Component

The radiation-sensitive composition may also comprise, in addition tothe components (A) to (C), optional components such as a compound thatmay be a ligand, a surfactant, and the like.

Compound that May be Ligand

The compound that may be a ligand to be used in the radiation-sensitivecomposition is exemplified by a compound that may be a polydentateligand or a bridging ligand (hereinafter, may be also referred to as“compound (II)”) and the like. Examples of the compound (II) includecompounds similar to those exemplified as the compounds that may beadded upon the hydrolytic condensation reaction in the synthesisprocedure of the particles (A), and the like.

In the case in which the radiation-sensitive composition contains thecompound (II), the upper limit of the content of the compound (II) withrespect to the total solid content in the radiation-sensitivecomposition is preferably 10% by mass, more preferably 3% by mass, andfurther more preferably 1% by mass.

Surfactant

The surfactant which may be used in the radiation-sensitive compositionis a component that exhibits the effect of improving coating properties,striation and the like. Examples of the surfactant include: nonionicsurfactants such as polyoxyethylene lauryl ether, polyoxyethylenestearyl ether, polyoxyethylene oleyl ether, polyoxyethylenen-octylphenyl ether, polyoxyethylene n-nonylphenyl ether, polyethyleneglycol dilaurate and polyethylene glycol distearate; and the like.Examples of a commercially available product of the surfactant includeKP341 (manufactured by Shin-Etsu Chemical Co., Ltd.), Polyflow No. 75and Polyflow No. 95 (each manufactured by Kyoeisha Chemical Co., Ltd.),EFTOP EF301, EFTOP EF303 and EFTOP EF352 (each manufactured by TochemProducts Co. Ltd.), Megaface F171 and Megaface F173 (each manufacturedby DIC Corporation), Fluorad FC430 and Fluorad FC431 (each manufacturedby Sumitomo 3M Limited), ASAHI GUARD AG710, Surflon S-382, SurflonSC-101, Surflon SC-102, Surflon SC-103, Surflon SC-104, Surflon SC-105and Surflon SC-106 (each manufactured by Asahi Glass Co., Ltd.), and thelike.

Preparation Method of Radiation-Sensitive Composition

The radiation-sensitive composition may be prepared, for example, bymixing the particles (A), the acid generator (B) and the solvent (C), aswell as the other optional component that may be added as needed, at acertain ratio, preferably followed by filtering a mixture thus obtainedthrough a membrane filter having a pore size of approximately 0.2 μm.The lower limit of the solid content concentration of theradiation-sensitive composition is preferably 0.1% by mass, morepreferably 0.5% by mass, still more preferably 1% by mass, andparticularly preferably 3% by mass. The upper limit of the solid contentconcentration is preferably 50% by mass, more preferably 30% by mass,still more preferably 15% by mass, and particularly preferably 7% bymass.

Pattern-Forming Method

The pattern-forming method comprises: applying the radiation-sensitivecomposition on one face side of a substrate (hereinafter, may be alsoreferred to as “applying step”); exposing a film obtained by theapplying (hereinafter, may be also referred to as “exposing step”); anddeveloping the film exposed (hereinafter, may be also referred to as“developing step”). The radiation-sensitive composition described aboveis employed in the pattern-forming method, and therefore the method isable to form with high sensitivity a pattern superior in resolution.Hereinafter, each step is explained.

Applying Step

In this step, the radiation-sensitive composition is applied on one faceside of a substrate to form a film. Specifically, the film is formed byapplying the radiation-sensitive composition such that the resultingfilm has a desired thickness, followed by prebaking (PB) to volatilizethe solvent and the like in the radiation-sensitive composition asneeded. A procedure for applying the radiation-sensitive composition isnot particularly limited, and an appropriate application procedure suchas spin-coating, cast coating, roller coating, etc. may be employed.Examples of the substrate include a silicon wafer, a wafer coated withaluminum, and the like. It is to be noted that an organic or inorganicantireflective film may also be formed on the substrate in order tomaximize potential of the radiation-sensitive composition.

The lower limit of an average thickness of the film to be formed in thepresent step is preferably 1 nm, more preferably 5 nm, further morepreferably 10 nm, and particularly preferably 20 nm. Meanwhile, theupper limit of the average thickness is preferably 1,000 nm, morepreferably 200 nm, further more preferably 100 nm, and particularlypreferably 70 nm.

The lower limit of the temperature for the PB is generally 25° C.,preferably 40° C., more preferably 60° C., and further more preferably80° C. The upper limit of the temperature for the PB is generally 160°C., preferably 140° C., and more preferably 120° C. The lower limit ofthe time period for the PB is generally 5 sec, and preferably 10 sec.The upper limit of the time period for the PB is generally 600 sec, andpreferably 300 sec.

In this step, in order to inhibit an influence of basic impurities,etc., in the environmental atmosphere, for example, a protective filmmay be provided on the film formed. Furthermore, in the case ofconducting liquid immersion lithography in the exposing step asdescribed later, in order to avoid a direct contact between a liquidimmersion medium and the film, a protective film for liquid immersionmay also be provided on the film formed.

Exposure Step

In this step, the film obtained by the applying is exposed.Specifically, for example, the film is irradiated with a radioactive raythrough a mask having a predetermined pattern. In this step, irradiationwith a radioactive ray through a liquid immersion medium such as water,i.e., liquid immersion lithography, may be employed as needed. Examplesof the radioactive ray for the exposure include: electromagnetic wavessuch as visible light rays, ultraviolet rays, far ultraviolet rays,extreme ultraviolet rays (EUV, wavelength: 13.5 nm), X-rays and γradiations; charged particle rays such as electron beams and α-rays; andthe like. Of these, EUV and electron beams are preferred in light ofincreasing the secondary electrons generated from the particles (A)having absorbed the radioactive ray.

It is preferred that the exposure is followed by post exposure baking(PEB), whereby the structural change of the particles (A), due to theacid generated by the acid generator (B) upon the exposure, is promotedin the light-exposed regions of the film. The PEB enables a differenceof solubility in a developer solution to be increased between thelight-exposed regions and the light-unexposed regions of the film. Thelower limit of the temperature for the PEB is preferably 50□, and morepreferably 70□. Meanwhile, the upper limit of the temperature for thePEB is preferably 180° C., and more preferably 130° C. The lower limitof the time period for the PEB is preferably 5 sec, and more preferably10 sec. The upper limit of the time period for the PEB is preferably 600sec, and more preferably 300 sec.

Development Step

In this step, the exposed film is developed by using a developersolution. A predetermined pattern is thereby formed. Examples of thedeveloper solution include an alkaline aqueous solution, an organicsolvent-containing liquid, and the like. In the case of using thealkaline aqueous solution as the developer solution, in general, apositive type pattern can be obtained. On the other hand, in the case ofusing the organic solvent-containing liquid as the developer solution,in general, a negative type pattern can be obtained. As the developersolution, the organic solvent-containing liquid is preferred in light ofdevelopability and the like.

Examples of the alkaline aqueous solution include: alkaline aqueoussolutions prepared by dissolving at least one alkaline compound such assodium hydroxide, potassium hydroxide, sodium carbonate, sodiumsilicate, sodium metasilicate, aqueous ammonia, ethylamine,n-propylamine, diethylamine, di-n-propylamine, triethylamine,methyldiethylamine, ethyldimethylamine, triethanolamine,tetramethylammonium hydroxide (TMAH), pyrrole, piperidine, choline,1,8-diazabicyclo-[5.4.0]-7-undecene and1,5-diazabicyclo-[4.3.0]-5-nonene; and the like.

The lower limit of a content of the alkaline compound in the alkalineaqueous solution is preferably 0.1% by mass, more preferably 0.5% bymass, and further more preferably 1% by mass. The upper limit of thealkaline compound is preferably 20 parts by mass, more preferably 10parts by mass, and further more preferably 5 parts by mass.

As the alkaline aqueous solution, an aqueous TMAH solution is preferred,and a 2.38% by mass aqueous TMAH solution is more preferred.

Examples of an organic solvent in the organic solvent-containing liquidinclude organic solvents similar to those exemplified in connection withthe solvent (C) in the radiation-sensitive composition, and the like. Ofthese, a hydrocarbon solvent is preferred; an aliphatic hydrocarbonsolvent, an alicyclic hydrocarbon solvent, and an aromatic hydrocarbonsolvent are more preferred; hexane, decahydronaphthalene, and tolueneare further more preferred; and a mixed solvent of hexane and toluene isparticularly preferred.

The lower limit of a content of the organic solvent in the organicsolvent-containing liquid is preferably 80% by mass, more preferably 90%by mass, further more preferably 95% by mass, and particularlypreferably 99% by mass. When the content of the organic solvent fallswithin the above range, a further improvement of a contrast of the rateof dissolution in the developer solution between the light-exposedregions and the light-unexposed regions is enabled. Examples ofcomponents other than the organic solvent in the organicsolvent-containing liquid include water, silicone oil, and the like.

An appropriate amount of a surfactant may be added to the developersolution as needed. As the surfactant, for example, an ionic or nonionicfluorochemical surfactant, a silicone surfactant, and the like may beused.

Examples of the development procedure include: a dipping procedure inwhich the substrate is immersed for a given time period in the developersolution charged in a container; a puddle procedure in which thedeveloper solution is placed to form a dome-shaped bead by way of thesurface tension on the surface of the substrate for a given time periodto conduct a development; a spraying procedure in which the developersolution is sprayed onto the surface of the substrate; a dynamicdispensing procedure in which the developer solution is continuouslyapplied onto the substrate that is rotated at a constant speed whilescanning with a developer solution-application nozzle at a constantspeed; and the like.

It is preferred that, following the development, the substrate is rinsedby using a rinse agent such as water, alcohol, etc., and then dried. Aprocedure for the rinsing is exemplified by a procedure of continuouslyapplying the rinse agent onto the substrate that is rotated at aconstant speed (spin-coating procedure), a procedure of immersing thesubstrate for a given time period in the rinse agent charged in acontainer (dipping procedure), a procedure of spraying the rinse agentonto the surface of the substrate (spraying procedure), and the like.

EXAMPLES

Hereinafter, the present invention is explained in detail by way ofExamples, but the present invention is limited to these Examples.Measuring methods for physical properties in connection with theExamples are shown below.

Average Particle Diameter

The average particle diameter of the particles (A) was measured by a DLSmethod using a light scattering measurement device (“Zetasizer Nano ZS”available from Malvern Instruments Ltd.).

Van Der Waals Volume

The van der Waals volume was calculated by obtaining a stable structurein accordance with the PM3 method using WinMOPAC (Ver. 3.9.0, availablefrom Fujitsu Limited).

(A) Particles

The organic acids (a) and the metal-containing compounds (b) used forsynthesis of the particles (A) are shown below.

Organic Acid (a)

a-1: methacrylic acid (pKa: 4.66)

a-2: tiglic acid (pKa: 4.96)

a-3: benzoic acid (pKa: 4.21)

Metal-Containing Compound (b)

b-1: zinc acetate dihydrate

b-2: zinc(I) isopropoxide

b-3: antimony(III) isopropoxide

b-4: tetraethoxysilane

b-5: zirconium(IV) isopropoxide

b-6: hafnium(IV) isopropoxide

b-7: boron(III) ethoxide

b-8: aluminum(III) isopropoxide

b-9: gallium(III) isopropoxide

b-10: thallium(I) ethoxide

b-11: germanium(IV) isopropoxide

b-12: bismuth(III) isopropoxide

b-13: tellurium(IV) isopropoxide

Synthesis Example 1

1.9 g of the compound (a-1) and 1.7 g of the compound (b-1) weredissolved in 40.0 g of ethyl acetate. 2.2 ml of triethylamine was addeddropwise to a solution thus obtained, and then heated at 65° C. for 2hrs. The reaction solution was washed with hexane and then dried to giveparticles (A-1) comprising principally: the metal atoms; and the ligandderived from the organic acid. The average particle diameter of theparticles (A-1) was 1.6 nm.

Synthesis Example 2

1.9 g of the compound (a-3) and 1.7 g of the compound (b-1) weredissolved in 40.0 g of ethyl acetate. 2.2 ml of triethylamine was addeddropwise to a solution thus obtained, and then heated at 65° C. for 2hrs. The reaction solution was washed with hexane and then dried to giveparticles (A-2) comprising principally: the metal atoms; and the ligandderived from the organic acid. The average particle diameter of theparticles (A-2) was 1.8 nm.

Synthesis Example 3

2.0 g of the compound (a-2) and 1.5 g of the compound (b-2) weredissolved in 15 ml of tetrahydrofuran. The resulting solution was heatedat 65° C. for 21 hrs. The reaction solution was washed with hexane andthen dried to give particles (A-3) comprising principally: the metalatoms; and the ligand derived from the organic acid. The averageparticle diameter of the particles (A-3) was 1.7 nm.

Synthesis Example 4

8.0 g of the compound (a-1) and 1.5 g of the compound (b-3) were mixedand then heated at 65° C. for 21 hrs. The reaction solution was washedwith ultra pure water and acetone and then dried to give particles (A-4)comprising principally: the metal atoms; and the ligand derived from theorganic acid. The average particle diameter of the particles (A-4) was2.0 nm.

Synthesis Example 5

1.9 g of the compound (a-3), 0.5 g of the compound (b-1), and 1.2 g ofthe compound (b-4) were dissolved in 40.0 g of ethyl acetate. 2.2 ml oftriethylamine was added dropwise to a solution thus obtained, and thenheated at 65° C. for 8 hrs. The reaction solution was washed with hexaneand then dried to give particles (A-5) comprising principally: the metalatoms; and the ligand derived from the organic acid. The averageparticle diameter of the particles (A-5) was 2.3 nm.

Synthesis Example 6

2.0 g of the compound (a-3) and 1.7 g of the compound (b-5) weredissolved in 15 ml of tetrahydrofuran. The resulting solution was heatedat 65° C. for 4 hrs. The reaction solution was washed with ultra purewater and then dried to give particles (A-6) comprising principally: themetal atoms; and the ligand derived from the organic acid. The averageparticle diameter of the particles (A-6) was 2.1 nm.

Synthesis Example 7

8.0 g of the compound (a-1) and 1.5 g of the compound (b-6) were mixedand then heated at 65° C. for 18 hrs. The reaction solution was washedwith ultra pure water and then dried to give particles (A-7) comprisingprincipally: the metal atoms; and the ligand derived from the organicacid. The average particle diameter of the particles (A-7) was 2.1 nm.

Synthesis Example 8

2.0 g of the compound (a-2) and 1.5 g of the compound (b-7) weredissolved in 15 ml of tetrahydrofuran. The resulting solution was heatedat 65° C. for 8 hrs. The reaction solution was washed with hexane andthen dried to give particles (A-8) comprising principally: the metalatoms; and the ligand derived from the organic acid. The averageparticle diameter of the particles (A-8) was 2.1 nm.

Synthesis Example 9

8.0 g of the compound (a-1) and 1.5 g of the compound (b-8) were mixedand then heated at 65° C. for 12 hrs. The reaction solution was washedwith ultra pure water and then dried to give particles (A-9) comprisingprincipally: the metal atoms; and the ligand derived from the organicacid. The average particle diameter of the particles (A-9) was 2.4 nm.

Synthesis Example 10

1.5 g of the compound (a-3) and 1.5 g of the compound (b-9) weredissolved in 15 ml of tetrahydrofuran. The resulting solution was heatedat 65° C. for 8 hrs. The reaction solution was washed with hexane andthen dried to give particles (A-10) comprising principally: the metalatoms; and the ligand derived from the organic acid. The averageparticle diameter of the particles (A-10) was 2.2 nm.

Synthesis Example 11

8.0 g of the compound (a-1) and 1.5 g of the compound (b-10) were mixedand then heated at 65° C. for 10 hrs. The reaction solution was washedwith ultra pure water and then dried to give particles (A-11) comprisingprincipally: the metal atoms; and the ligand derived from the organicacid. The average particle diameter of the particles (A-11) was 2.1 nm.

Synthesis Example 12

2.5 g of the compound (a-3) and 1.5 g of the compound (b-11) weredissolved in 15 ml of tetrahydrofuran. The resulting solution was heatedat 65° C. for 18 hrs. The reaction solution was washed with hexane andthen dried to give particles (A-12) comprising principally: the metalatoms; and the ligand derived from the organic acid. The averageparticle diameter of the particles (A-12) was 2.3 nm.

Synthesis Example 13

2.0 g of the compound (a-2) and 1.5 g of the compound (b-12) weredissolved in 20 ml of tetrahydrofuran. The resulting solution was heatedat 65° C. for 12 hrs. The reaction solution was washed with hexane andthen dried to give particles (A-13) comprising principally: the metalatoms; and the ligand derived from the organic acid. The averageparticle diameter of the particles (A-13) was 2.4 nm.

Synthesis Example 14

8.0 g of the compound (a-1) and 1.5 g of the compound (b-13) were mixedand then heated at 65° C. for 10 hrs. The reaction solution was washedwith ultra pure water and then dried to give particles (A-14) comprisingprincipally: the metal atoms; and the ligand derived from the organicacid. The average particle diameter of the particles (A-14) was 2.0 nm.

Synthesis Example 15

1.7 g of the compound (b-1) was dissolved in 20.0 g of ethyl acetate.2.2 ml of triethylamine was added dropwise to a solution thus obtained,and then heated at 65° C. for 2 hrs. The reaction solution was washedwith hexane and then dried to give particles (A-15) comprisingprincipally: the metal atoms; and oxygen atoms. The average particlediameter of the particles (A-15) was 2.8 nm.

Preparation of Radiation-Sensitive Composition

The acid generating agent (B) and the solvent (C) which were used in thepreparation of the radiation-sensitive resin composition are shownbelow.

(B) Acid Generating Agent

B-1: N-(trifluoromethylsulfonyloxy)-1,8-naphthalimide (van der Waalsvolume of generated acid: 0.84×10⁻²⁸ m³)

B-2: triphenylsulfonium trifluoromethanesulfonate (van der Waals volumeof generated acid: 0.84×10⁻²⁸ m³)

B-3: 4-cyclohexylsulfonylphenyldiphenylsulfonium5,6-di(cyclohexyloxycarbonyl)norbornane-2-sulfonate (van der Waalsvolume of generated acid: 3.80×10⁻²⁸ m³)

B-4: triphenylsulfonium6-(adamantane-1-ylcarbonyloxy)-1,1,2,2-tetrafluorohexane-1-sulfonate(van der Waals volume of generated acid: 3.34×10⁻²⁸ m³)

(C) Solvent

C-1: propylene glycol monomethyl ether acetate

C-2: propylene glycol monoethyl ether

Comparative Example 1

100 parts by mass of the particles (A-1) as the particles (A), 5 partsby mass of (B-1) as the acid generating agent (B), and 5 parts by massof (C-1) as the solvent (C) were mixed to give a mixed liquid having asolid content concentration of 5% by mass. The mixed liquid thusobtained was filtered through a membrane filter having a pore size of0.20 μm, to thereby prepare a radiation-sensitive composition (R-1).

Comparative Examples 2 to 10 and Examples 1 to 13

Respective radiation-sensitive compositions were prepared by a similaroperation to that of Comparative Example 1 except that the type and thecontent of each component used were as shown in Table 1 below.

A percentage content of the first metal atom with respect to total metalatoms in the radiation-sensitive compositions (R-1) to (R-4) and (R-8)to (R-23) is 100 atomic %. A percentage content of the first metal atomin the radiation-sensitive composition (R-5) is 16 atomic %. Apercentage content of the first metal atom in the radiation-sensitivecompositions (R-6) and (R-7) is 0 atomic %. It is to be noted that thepercentage content of the first metal atom is an estimated value basedon a hypothesis that: the metal atoms comprised in each of the radiationsensitive compositions are all derived from the particles (A); and uponsynthesis of the particles (A), each identical type of metal atomscomprised in the metal-containing compound (b) has been incorporated ata given ratio. Specifically, the percentage content of the first metalatom is a value obtained by a formula of: 100×R_(a)/R_(A), wherein R_(A)is the number of all the metal atoms comprised in the metal-containingcompound (b) used for synthesis of the particles (A), and R_(B) is thenumber of the first metal atoms comprised in the metal-containingcompound (b).

TABLE 1 Radiation- (A) Particles (B) Acid generating agent sensitiveContent Content (C) Solvent composition Type (parts by mass) Type (partsby mass) Type Comparative Example 1 R-1 A-1 100 B-1  5 C-1 ComparativeExample 2 R-2 A-2 100 B-1 10 C-1/C-2* Comparative Example 3 R-3 A-3 100B-1  5 C-1 Comparative Example 4 R-4 A-4 100 B-2 10 C-1 ComparativeExample 5 R-5 A-5 100 B-2  5 C-1 Comparative Example 6 R-6 A-6 100 B-3 5 C-1 Comparative Example 7 R-7 A-7 100 B-4  5 C-2 Comparative Example8 R-8 A-1 100 — — C-1 Comparative Example 9 R-9 A-2 100 — — C-1/C-2*Comparative Example 10 R-10 A-3 100 — — C-1 Example 1 R-11 A-1 100 B-3 5 C-1 Example 2 R-12 A-1 100 B-4  5 C-1 Example 3 R-13 A-2 100 B-4 10C-1/C-2* Example 4 R-14 A-3 100 B-3 10 C-1 Example 5 R-15 A-4 100 B-3  5C-1 Example 6 R-16 A-8 100 B-4  5 C-1 Example 7 R-17 A-9 100 B-3  5 C-1Example 8 R-18 A-10 100 B-4  5 C-2 Example 9 R-19 A-11 100 B-3  5C-1/C-2* Example 10 R-20 A-12 100 B-4  8 C-1 Example 11 R-21 A-13 100B-3  8 C-1 Example 12 R-22 A-14 100 B-4 10 C-1 Example 13 R-23 A-15 100B-4 10 C-1 *Mass ratio of C-1 to C-2 is 1:1

Pattern Formation Comparative Example 1

The radiation-sensitive composition (R-1) prepared as described abovewas spin-coated onto a silicon wafer by a simplified spin coater, andthen subjected to PB at 100° C. for 60 sec to form a film having anaverage thickness of 50 nm. Next, the film was irradiated with anelectron beam using an electron beam writer (“JBX-9500FS” available fromJEOL Ltd.) to permit patterning. After the irradiation with the electronbeam, the film was subjected to PEB at 100° C. for 60 sec, and to adevelopment carried out with an organic solvent (a mixed solvent oftoluene and hexane in a volume ratio of 1:1), followed by drying,whereby a negative type pattern was formed.

Comparative Examples 2 to 10 and Examples 1 to 13

Patterns were formed by using respective radiation-sensitivecompositions by a similar operation to that of Comparative Example 1except that the processes used were as shown in Table 2 below. Thesymbol “-” in Table 2 indicates that the corresponding process was notused.

Evaluations

The patterns thus formed were evaluated for the sensitivity and limitresolution by the method described below. The results are shown in Table2.

Sensitivity

An exposure dose, at which a line and space pattern (1L 1S) configuredwith line parts having a line width of 100 nm and space parts of 100 nmformed by neighboring line parts was formed to give a line width of 1:1,was defined as an “optimal exposure dose”, and the “optimal exposuredose” was defined as “sensitivity” (μC/cm²). The smaller value indicatessuperior sensitivity; and the sensitivity of no greater than 60 μC/cm²may be evaluated to be favorable, and the sensitivity of greater than 60μC/cm² may be evaluated to be unfavorable.

Limit Resolution

Line and space patterns (1L 1S) were formed to have various line widths,and a half-pitch of the pattern in which a total of the line widths andthe space widths was the smallest among the line and space patternshaving the line width of 1:1 being maintained was defined as a limitresolution (nm). The smaller value indicates superior limit resolution;and the resolution of no greater than 50 nm may be evaluated to befavorable, and the limit resolution of greater than 50 nm may beevaluated to be unfavorable.

TABLE 2 Radiation- PEB Limit sensitive PB temperature Sensitivityresolution composition (° C.) (° C.) (μC/cm²) (nm) Comparative R-1 100100 55 55 Example 1 Comparative R-2 100 — 55 55 Example 2 ComparativeR-3 100 — 55 60 Example 3 Comparative R-4 100 100 55 60 Example 4Comparative R-5 100 — 70 70 Example 5 Comparative R-6 100 — 60 65Example 6 Comparative R-7 100 100 65 65 Example 7 Comparative R-8 100100 60 60 Example 8 Comparative R-9 100 100 65 60 Example 9 ComparativeR-10 100 — 65 65 Example 10 Example 1 R-11 100 100 50 35 Example 2 R-12100 100 55 40 Example 3 R-13 100 100 55 45 Example 4 R-14 100 — 55 45Example 5 R-15 100 — 55 50 Example 6 R-16 100 100 50 40 Example 7 R-17100 100 55 50 Example 8 R-18 100 100 50 40 Example 9 R-19 100 — 50 45Example 10 R-20 100 — 45 40 Example 11 R-21 100 — 50 45 Example 12 R-22100 — 50 40 Example 13 R-23 100 — 50 50

From the results shown in Table 2, it was confirmed that by using anacid generator that generates an acid having a van der Waals volume ofno less than 2.0×10⁻²⁸ m³, in combination with the particles thatcomprise as a principal component a metal oxide comprising the firstmetal atom, formation of a fine pattern was enabled with superiorsensitivity and resolution. It is to be noted that an exposure to anelectron beam is generally known to give a tendency similar to that inthe case of the exposure to EUV. Therefore, the radiation-sensitivecomposition of the embodiments of the present invention is expected tobe superior in sensitivity and resolution also in the case of anexposure to EUV.

The radiation-sensitive composition and the pattern-forming methodaccording to the embodiments of the present invention enable a patternsuperior in resolution to be formed with high sensitivity. Therefore,these can be suitably used for a processing process of semiconductordevices, and the like, in which further progress of miniaturization isexpected in the future.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

What is claimed is:
 1. A radiation-sensitive composition comprising:particles comprising a metal oxide as a principal component; aradiation-sensitive acid generator; and an organic solvent, wherein: themetal oxide comprises at least one metal atom selected from the groupconsisting of a zinc atom, a boron atom, an aluminum atom, a galliumatom, a thallium atom, a germanium atom, an antimony atom, a bismuthatom, and a tellurium atom; the number of the at least one metal atom inthe particles is from 2 to 6; a van der Waals volume of an acidgenerated from the radiation-sensitive acid generator is no less than2.0×10⁻²⁸ m³; and a percentage content of the at least one metal atomwith respect to total metal atoms in the radiation-sensitive compositionis no less than 50 atomic %.
 2. The radiation-sensitive compositionaccording to claim 1, wherein a content of the radiation-sensitive acidgenerator with respect to a total solid content in theradiation-sensitive composition is no less than 1% by mass and nogreater than 40% by mass.
 3. The radiation-sensitive compositionaccording to claim 2, wherein an average particle diameter of theparticles is no greater than 20 nm.
 4. The radiation-sensitivecomposition according to claim 1, wherein an average particle diameterof the particles is no greater than 20 nm.
 5. The radiation-sensitivecomposition according to claim 1, wherein the particles further comprisea ligand derived from an organic acid.
 6. The radiation-sensitivecomposition according to claim 5, wherein the organic acid is at leastone selected from the group consisting of a carboxylic acid, a sulfonicacid, a sulfinic acid, an organic phosphinic acid, an organic phosphonicacid, a phenol, an enol, a thiol, an acid imide, an oxime, and asulfonamide.
 7. The radiation-sensitive composition according to claim5, wherein the organic acid is a carboxylic acid.
 8. Theradiation-sensitive composition according to claim 5, wherein theorganic acid is at least one selected from the group consisting ofmethacrylic acid, tiglic acid, benzoic acid, m-toluic acid, o-toluicacid, and 3-iodobenzoic acid.
 9. The radiation-sensitive compositionaccording to claim 5, wherein a percentage content of the ligand derivedfrom the organic acid is from 40 to 95% by mass.
 10. Theradiation-sensitive composition according to claim 1, wherein theradiation-sensitive acid generator is an onium salt.
 11. Theradiation-sensitive composition according to claim 10, wherein the oniumsalt is a sulfonium salt.
 12. The radiation-sensitive compositionaccording to claim 1, wherein the percentage content of the at least onemetal atom with respect to the total metal atoms in theradiation-sensitive composition is no less than 80 atomic %.
 13. Theradiation-sensitive composition according to claim 1, wherein the vander Waals volume of an acid generated from the radiation-sensitive acidgenerator is no less than 3.0×10⁻²⁸ m³.
 14. A pattern-forming methodcomprising: applying the radiation-sensitive composition according toclaim 1 to form a film on a substrate; exposing the film; and developingthe film exposed.
 15. The pattern-forming method according to claim 14,wherein a developer solution used in the developing is an alkalineaqueous solution.
 16. The pattern-forming method according to claim 15,wherein a radioactive ray used in the exposing is an extreme ultravioletray or an electron beam.
 17. The pattern-forming method according toclaim 14, wherein a developer solution used in the developing is anorganic solvent-containing liquid.
 18. The pattern-forming methodaccording to claim 17, wherein a radioactive ray used in the exposing isan extreme ultraviolet ray or an electron beam.
 19. The pattern-formingmethod according to claim 14, wherein a radioactive ray used in theexposing is an extreme ultraviolet ray or an electron beam.
 20. Theradiation-sensitive composition according to claim 5, wherein theradiation-sensitive composition consists of: the particles; theradiation-sensitive acid generator; the solvent; optionally, a ligandother than the ligand derived from the organic acid; and optionally, asurfactant.